Electronic shutter system

ABSTRACT

An electronic shutter system is comprised of a photoelectric exposure timer and includes an adjustable timer circuit. The exposure timer triggers the adjustable timer which adds an additional amount of exposure time before shutter closure to compensate for delay in shutter opening do to shutter blade overlap.

United States Patent 15] 3,683,767 Sahara [4 1 Aug. 15, 1972 ELECTRONICSHUTTER SYSTEM [56] References Cited [72] Inventor: Masayoshi Sahara,Sakai,Japan UNITED STATES PATENTS [73] Assignee: Minolta CameraKabushiki Kaisha, 3,5 0,729 3/1970 Rentschler et al ..95/l0 CT OsakaPrefecture, Japan P E 8 IS M th rimary xamineramue at ews [22] Filed:June 1971 Assistant Examiner-Russell E. Adams, Jr. 2 App} 55 413Attorney-Craig and Antonelli [30] F A li ti Pr 't Data I [57.] ABSTRACTorelgn. pp ca on on y 'An electronic shutter system is comprised of aphotoelectric exposure timer and includes an adjusta- June 22, 1970Japan ..45/54650 ble timer circuit The exposure timer triggers thejustable timer which adds an additional amount of ex- 2% ilSil ..95/10CT,G953/51; EB posure time before Shutter closure to compensate for 1 zi3 delay in shutter opening do to shutter blade overlap.

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PATENTEDAUG 15 I972 SHEET 1 OF 2 M95 AA @385 2952 0 f I2 i3 FIG. I

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INVENTOR MASAYOSHI SAHARA Y mow HLQQ ATTORNFYS PATENTED Aus 15 I972SHEET 2 OF 2 FIG. 3

INVENTOR [I0 MASAYOSHI SAHARA BY mil amtmm m AHORNEYS ELECTRONIC SHUTTERSYSTEM BACKGROUND OF THE INVENTION The present invention relates to anelectronic shutter circuit capable of adjusting the errors in theexposure,

which are caused by the difference between the exposure time determinedby an electrical exposure measuring circuit and the desired exposure ofthe film.

Generally, in a shutter which gives an exposure to the film by themovement of two light-shielding members, that move in the same directionwith a time lag proportional to the desired exposure time, such as atwo-curtain focal plane shutter or rotary-mirror shutter, said twolight-shielding members are partially overlapped each other during theshutter charging, as well as, prior to the start of operation, so asmainly to prevent light coming through these two members. Therefore, thestarting positions of these two light-shielding members are different,and the following light-shielding member (hereinafter referred to asfollowing member) must be started after starting of the firstlight-shielding member (hereinafter referred to as leading member) toallow a time difference for the desired exposure time plus the timerequired for release the overlapping of the two members.

For example, in the case of a two-curtain focal plane shutter, themovement of the shutter curtains can be plotted as shown in FIG. 1. InFIG. 1, the abscissaindicates the time elapsed 1, taking the startingposition of the leading curtain as its starting point, and the ordinateindicates the distance of movement of the shutter curtains, taking thestarting position of the end of the leading curtain as its startingpoint 0. Since the end of the leading curtain and the top of thefollowing curtain are overlapped prior to the start of a focal planeshutter, the starting position of the top of the following curtain isindicated at the position S against the starting position of the end ofthe leading curtain S and the distance between the positions a and abecomes the opening for exposuring film, i.e., exposure aperture. Thecurve 1 shows the movement of the end of the leading curtain and thecurves 2, 3, 4, and show the movements of the top of the followingcurtain corresponding to various exposure times, and t t t and show thetime between the start of the leading curtain and that of the followingcurtain.

Generally, in such a two-curtain focal plane shutter, each shuttercurtain is accelerated until the end of the leading curtain or the topof the following curtain reaches the exposure aperture, and each shuttercurtain shows nearly parallel movement curves while passing across theexposure aperture, and the distance between the curves in the directionof the axis of the abscissas (for example, te and te becomes the actualexposure time. Therefore, if the following curtain starts moving rightafter the start of the leading curtain at the point 2 the movement curveof the top of the following curtain coincides with the movement curve ofthe end of the leading curtain at the exposure aperture; in other words,if the difference in the starts of the two curtains is smaller than t,,the film in the camera is not exposed at all.

Thus, the film exposure time T and the time difference t, which existsbetween the starts of the two shutter curtains have the followingrelationship:

wherein t, is dependent of the degree of the overlapping of the twoshutter curtains and their movement characteristics and is a constantparticular to individual shutter. Nonnally, the value of t, is around4/l,000 to 5/ 1,000 second which is about 4 to 5 times as long as theshortest exposure time of l/ l ,000 second common to normal focal planeshutters. In other words, the time difference t, between the starts ofthe respective shutter curtains shall be equal to the exposure time Tplus I, which is particular to individual shutter.

On the other hand, the conventional electronic shutter is constructed insuch a way that the exposure time is measured at the start of theshutter opening operation, and the shutter closing operation startsafter the lapse of the proper exposure time. Accordingly, it is requiredto give some adjustment responding to the particular additional time(equaling t in said example of a two-curtain focal plane shutter due tothe overlapping of the light-shielding members, in order to apply theconventional electronic shutter circuit to the shutter consisting of aleading member and a following member as aforementioned. Theconventional means for this adjustment proposed by the prior art is suchthat the exposure time measurement starts only when the end of theleading member moves to the position where the overlapping with thefollowing member is released by mechanical means; however, suchmechanical means make the construction of the shutter complicated andalso the adjustment of the errors of the additional times particular toindividual cameras become difficult, and said adjustment quantities alsotend to bear variations (spread) among cameras. As a result, theadjustment of high accuracy becomes impossible and especially,considerable exposure error in high-speed picture taking tends toresult.

Also, in conventional electronic shutter circuits, there are variations(spreads) among cameras as to the time from the start of the shutteropening operation to the opening of the count switch of the controlcircuit to start counting the exposure time obtained by the lightexposure measuring circuit, as well as, the time from the generation ofshutter closing signal in the controls circuit to the actual operationof the closing members of the shutter, which times are difficult toadjust.

SUMMARY OF THE INVENTION An objective of the present invention is toprovide an electronic shutter, which is free from the aforementioneddisadvantages of conventional electronic shutters, and is capable ofadjusting the additional times particular to individual shutters anderrors of time in the interlocking system between the control circuitand the mechanical operating members, with high accuracy. To practicethis objective, the present invention incorporates an additional timercircuit, to provide the required additional time to the exposure timecontrol circuit, which comprises a control circuit for the controllingthe time responding to the brightness of an photographic object, to theopening of the diaphragm of the picture-taking lens and to the filmsensitivity, and an electromagnet for starting the closing operation ofthe shutter. By this circuit construction, the shutter closing operationstarts after the lapse of a proper exposure time measured by saidcontrol circuit plus a time lag added by said timer circuit, wherein theadditional time lag added by said timer circuit is made to beadjustable.

BRIEF DESCRIPTION OF THE DRAWDIGS FIG. I is a graph indicating themovement of the shutter curtains in a focal plane shutter;

FIGS. 2 and 3 and 4 are schematic circuit diagrams of examples ofelectronic shutter circuit embodying the present invention, wherein thecircuit elements for the same function are shown with common referencecharacters.

DETAILED DESCRIPTION In FIG. 2, P is a photoconductive element, C, is acapacitor to constitute a first delay circuit together with saidphotoconductive element P, and SW, is a count-starting switch connectedto constitute a shortcircuiting path for the capacitor C, when closed.Transistors Tr, and Tr, form a switching circuit wherein one transistorbecomes conductive as the other transistor becomes non-conductive, andthe transistor Tr, is an amplifying transistor. A capacitor C, connectedbetween the emitter and the collector of the transistor Tr, forms thesecond delay circuit together with a variable resistor or semi-fixedresistor VR, connected in the collector circuit of said transistor Tr,.Transistors Tr, and Tr constitute a second switching circuit whichresponds to the voltage across the variable resistor VR,, and thetransistor Tr, is an amplifying transistor. An electromagnet Mg isconnected in the output circuit of the transistor Tr,, whichelectromagnet Mg starts the closing operation of the shutter, by knownmeans not shown in figure, when the switching circuit comprising thetransistor Tr and Tr is reversed. E is a DC power supply, SW, is a powerswitch, and F is an optical filter to control the light incident on thephotoconductive element P, depending on the lens diaphragm opening andthe film sensitivity.

In such a circuit construction, when the power switch SW, is closed, thetransistors Tr and Tr, become conductive, since the transistor Tr, is inthe non-conductive state, because the capacitor C, is short-circuited bythe count starting switch SW,. Therefore, the transistor Tr, becomesnon-conductive and the transistors Tr and Tr, become conductive,whereupon the electromagnet Mg is excited, because only a very lowvoltage between the emitter and the collector of the transistor Tr,,which is in the conductive state, is applied across both ends of thecapacitor C,. This excited electromagnet holds holding members of theshutter closing mechanism, for example, the holding members of thefollowing curtains in a two-curtain focal plane shutter, in theirholding positions by known means. Subsequent to this, when the countswitch SW, is opened, being interlocked with the start of the openingmovement of the shutter, for example, the release of the landing curtainin a focal plane shutter and charging of the capacitor C, through thephotoconductive element P starts and, when the capacitor C, is chargedto a predetermined level after the lapse of a proper exposure timedetermined by the light resistance of the photoconductive element P andthe electrostatic capacitance of the capacitor C,, in other words, afterthe lapse of time equal to the desired exposure time, the transistor Tr,becomes conductive and the transistors Tr, and Tr, become non-conductiveand the capacitor C, is charged through the variable resistor VR,. Thus,the transistor Tr, works as a kind of shortcircuiting switch for thecapacitor C,. After the lapse of time determined by the resistance ofthe variable resistor VR, and the electrostatic capacitance of thecapacitor C,, the capacitor C, is charged to the predetermined value,the switching circuit comprising the transistors Tr, and Tr, is reversedmaking the transistor Tr, non-conductive, and electric current to theelectromagnet Mg is cut off. Accordingly, the holding of said shutterholding members isreleased and the shutter closing operation takesplace. Moreover, the value of the variable resistor VR, can be pre-setappropriately to respond to the additional time particular to theindividual camera. This additional time can be set as a value includingthe adjustment required against error.

FIG. 3 illustrates a schematic circuit diagram of another example of anelectronic shutter circuit embodying the present invention. Thedifference from the embodiment shown in FIG. 2 and that of FIG. 3 issuch that the emitter of the transistor Tr, is connected to theconnecting point of the variable resistors VR, and VR,, to whichvoltages divided by these two variable resistors are applied. Also, thevariable resistors VR, and VR, are set to certain values respectivelyresponding to the diaphragm opening of the camera lens and the filmsensitivity by known linking means not shown in figure. The relationshipamong the transistors Tr,, Tr, and Tr, is such that they form aswitching circuit, wherein the transistor Tr, is in conductive statewhen the transistors Tr, and Tr, are non-conductive, which circuitbecomes completely in the opposite state of the transistors whenreversed. The capacitor C, is connected in parallel with the variableresistor VR,.

In such a circuit construction, as in the case of FIG. 2, when the powerswitch SW, is closed and the transistor Tr, becomes conductive, thevoltage across both ends of the variable resistor VR,, as well as acrossthe capacitor C,, increase and the voltage between the base and theemitter of the transistor Tr, drops, making the transistor Tr,,non-conductive and hence, making the transistors Tr, and Tr, conductive.Then power is fed to the electromagnet Mg through the transistor Tr,,.After the opening of the count starting switch SW, and the lapse of apredetermined time, the capacitor C, is charged to the predeterminedvalue corresponding to the voltage divided by the variable resistors VR,and VR,, and then the on-ofi state of the switching circuit comprisingthe transistors Tr,, Tr, and Tr, is reversed and the transistor Tr,becomes non-conductive. whereupon, the electric charge stored in thecapacitor C, is discharged through the variable resistor VR, and, afterthe lapse of time corresponding to the resistance of said variableresistor VR, and the electrostatic capacitance of the capacitor C,, thecapacitor C, is discharged down to the predetermined level; and theswitching circuit comprising the transistors Tr,, and Tr is reversed andthe transistor Tr, becomes nonconductive to cut off the supply ofcurrent to the electromagnet Mg, and triggers the closing operation ofthe shutter.

FIG. 4 illustrates a schematic circuit diagram of a practical example ofan electronic shutter circuit embodying the present invention, which isa circuit made by adding a thermal error compensation circuit and anelectric voltage error compensation circuit and further inserting adifferential amplifier circuit between a first delay circuit containingthe photoconductive element and the transistor switching circuit, to thecircuit illustrated in FIG. 2, in order to increase the detectingaccuracy and stability of operation. In FIG. 4, Tr, and Tr aretransistors constituting a differential amplifier circuit. A transistorTr,,, to whose collector the emitters of the transistors Tr, and Tr areconnected, forms a constant current circuit to keep the total emittercurrent of said differential amplifier circuit constant and to maintainthe output of said differential amplifier circuit at a constant level,together with a transistor Tr the collector of which is connected to thebase of said transistor Tr VR, is a variable resistor to provide biasvoltage to the base of transistor Tr the base of which is connected tothe rotor terminal of the variable resistor VR and the resistance of itis set depending on, for instance, the film sensitivity. The filter F isconstituted to control the incident light of the photoconductive elementP depending on the value of camera-lensdiaphragm opening. Tr and Tr aretransistors to increase the number of adjusting steps for the variableresistor VR. responding to the film sensitivity, by raising the basevoltage of the transistors Tr and Tr A transistor Tr the collector ofwhich is connected to the collector of the transistor Tr, via the outputresistor R is for thermal compensation by the transistor Tr, whichconstitutes a switching circuit with the transistor Tr Tr is atransistor which constitutes, together with transistors Tr and Tr aswitching circuit, providing the function same as the circuit comprisingthe transistors Tr' Tr and Tr in FIG. 3. Transistor Tr connected in aseries with the voltage dividing resistors R and R is a thermalcompensation transistor for said transistor Tr An electromagnet Mg isconnected in the collector circuit of said transistor Tr In such acircuit construction, when the power switch SW is closed at the start ofthe shutter-opening opera tion, the capacitor C is short-circuited bythe count starting switch SW and the collector current of the transistorTr is very small. Therefore, the transistor Tr is non-conductive stateand, like the case of the circuit illustrated in FIG. 2, the capacitor Cis only charged slightly, the transistors Tr and Tr are in thenon-conductive state and the transistor Tr is in the conductive state.Accordingly, the electromagnet Mg is excited and the holding members ofthe shutter-closing mechanism are held in their holding positions. Bythe opening operation of the shutter, the count starting switch SW isopened and the capacitor C is charged through the photoconductiveelement P and, after the lapse of time equal to the proper exposure timedetermined by the filter F the film sensitivity and thecamera-lens-diaphragm opening, the capacitor C is charged to thepredetermined level. Then, the collector current of the transistor Trincreases suddenly and the output voltage increases, making thetransistor Tr conductive. Therefore, the transistor Tr, is cut off andthe capacitor C is charged through the variable resistor VR and when thecharging voltage reaches the predetermined value, the switching circuitcomprising the transistors Tr Tr and Tr is reversed and the supply ofpower to the electromagnet Mg is cut off, whereupon the shutter-closingoperation starts.

Now, the function of the foregoing embodiment against the fluctuation ofvoltage and temperature will be explained. The delay time of the seconddelay circuit comprising the variable resistor VR, and the capacitor Cin other words, the time required after the transistor Tr becomesnon-conductive state from conductive state until the transistor Trbecomes conductive state from non-conductive state, is defined as t thistime t can be considered as the time required for the charged. voltageof the capacitor C to become equal to the total voltage across both endsof the resistor R and the base-emitter voltage V of the transistor TrWhen the collector current of the transistor Tr in the conductive stateis set around lp.A and the collector current of the transistor Tr is setaround SOuA, the influence of the collector current of said transistorTr is negligibly small, and the following equation can be established:

and i is expressed by t G2 T 10g E If we set the circuit constant tosatisfy the following equation:

the equation (1) becomes an enn which means that the delay time t doesnot include any parameter of the power supply voltage and become freefrom fluctuation of the power supply voltage.

Now, consider the influence of the fluctuation in the characteristics oftransistors by the ambient temperature. As aforementioned, when thecollector current of the transistor Tr is set around Ill-A and thecollector current of the transistor Tr is set around SOuA, the followingvalue V, in the equation (3) changes normally at a rate of about -0.3 mVagainst the temperature change of 1 C, due to the difference of theoperating points of these transistors.

IBE17 BE14) camera operating conditions, said value V, changes aboutlmV. However, since the value of r /r r )E in the Equation (1) is in theorder of volts, said change of about ISmV is negligible, and by thecircuit construction as shown in FIG. 4, the delay time of the seconddelay circuit obtains stable performance characteristics against thefluctuation of both the supply voltage and the ambient temperature.

On the other hand, in the differential amplifier circuit, the stableperformance characteristics are always maintained by the control of theemitter current which is regulated by the constant voltate circuitcomprising the transistors Tr and Tr and the change in thecharacteristics of the switching transistor Tr connected to the outputstage of said differential amplifier circuit, is offset by that of thetransistor Tr and thus stable switching performance characteristics areprovided.

The embodiment of the present invention is not limited to the examplesmentioned above, but is provides the same effect even if the positionsof the photoconductive element P and the variable resistor VR areexchanged with each other in the circuit illustrated in FIG. 2. Also inthe circuit illustrated in FIG. 4, it is possible to control the startof charging to the capacitor C,, which is connected in series with thephotoconductive element P, by controlling with the switching circuitconnected as a next stage to the second delay circuit, when theelectromagnet Mg is connected to the output of the switching circuitwhich is controlled by the first delay circuit including thephotoconductive element P. Also, the type of the light measuring elementis not limited to the photoconductive element, but the delay circuitsand the switching circuits can be modified within a range correspondingto the objective of the present invention, and moreover, variousmodifications can be adopted for interlocking of the electronic circuitwith the shutteroperating mechanism depending on the requirements.

As aforementioned, the present invention enables the start of theshutter-closing operation by the operation of the electromagnet afterthe lapse of the delay time for the exposure corresponding to thebrightness of the photographic object plus the additional delay timecreated by the timer circuit. Therefore, it is possible to adjust thestarting time difference in the lightshielding members in response toparticular additional time sufficient to cover overlapping of thelight-shielding members by electronic means of high accuracy in theshutter where in the two light-shielding members move in the samedirection at a required time interval. Also, the additional time delayis easily controlled with high accuracy by electronic means; therefore,the error in the additional time particular to an individual camera andthe error in the interlocking time between the electronic circuit andthe shutter-operating mechanism can also be adjusted. Thus, anelectronic shutter of high accuracy without error can be furnished toeach camera, such accuracy having the significant effect of assuring theaccuracy even for the shortest shutter speed.

Also, the circuit of the present invention provides an electronicshutter of high accuracy to ordinary lens shutters by eliminating theerror in the control time particular to individual camera. In otherwords, by constituting a circuit for starting the shutter-openingoperation after the lapse of predetermined short time subsequent to theopening of the count starting switch, errors among cameras as to thetime required before starting switch and the time required before theshutter is actually closed after the shutter-closing signal is generatedby the electronic circuit, can be corrected by adjusting the additionaldelay time related to the timer circuit of the present invention.

I claim:

1. An electronic shutter system for controlling the opening and closingof a camera shutter comprising:

camera shutter control means, connected to said camera shutter, foreffecting the opening and closing thereof; I

a first control circuit, including first means, responsive to theapplication of input power thereto, for generating a shutter openingsignal;

a second control circuit, connected to said first control circuit,including second means, responsive to said shutter-opening signal, forapplying said shutter opening signal to said shutter control means, foreffecting the opening of said camera shutter, wherein said first controlcircuit further includes third means, coupled to said shutter controlmeans and being responsive to the commencement of the opening motion ofsaid camera shutter by said shutter control means, for generating afirst timing signal; and

wherein said second control circuit further includes fourth means,responsive to the generation of said first timing signal by said thirdmeans, for generating a second timing signal and supplying said secondtiming signal to said shutter control means,

whereby said camera shutter will be closed by the ap plication of saidsecond timing signal to said shutter control means, a period of timeafter the opening thereof.

2. An electronic shutter system according to claim 1, wherein saidshutter control means comprises an electromagnetic means connected tosaid shutter and wherein said third means of said first control circuitincludes a photoelectric element and a first capacitor connected inseries to form a first timing circuit and being responsive to thebrightness of a photographic object for controlling the characteristicsof said first timing signal.

3. An electronic shutter system according to claim 2, wherein saidfourth means of said second control circuit comprises a variableresistor and a second capacitor connected together to form a secondtiming circuit, the charging of said second capacitor being controlledby said first timing signal, and wherein said second control circuitincludes an output transistor switching circuit, the output of which isconnected to said electromagnetic means, responsive to the chargeaccumulation on said second capacitor, for effecting the energizationand de-energization of said electromagnetic means, whereby said shutterwill be opened and closed thereby.

4. An electronic shutter system according to claim 2, wherein saidfourth means of said second control circuit comprises a variableresistor and a second capacitor connected together to form a secondtiming signal, the discharging of said second capacitor being controlledby said first timing signal, and wherein said second control circuitincludes an output transistor switching circuit, the output of which isconnected to said electromagnetic means, responsive to the chargeaccumulation on said second capacitor, for effecting the energizationand de-energization of said electromagnetic means, whereby said shutterwill be opened and closed thereby.

5. An electronic shutter system according to claim 2, wherein said thirdmeans of said first control circuit further includes a differentialamplifier connected to said photoelectric element and coupled to saidsecond control circuit.

6. An electronic shutter system according to claim 5, wherein saidoutput transistor switching circuit further includes a compensationtransistor circuit connected thereto for effectively compensating saidoutput switching circuit against temperature variations therein.

7. An electronic switching system according to claim 5, wherein saiddifferential amplifier includes a compensation transistor circuit forprotecting said differential amplifier against the dependency thereof onvariations in the source voltage applied thereto.

8. An electronic shutter system according to claim 1, wherein said firstmeans of said first control circuit includes a first transistorswitching circuit connected between a source of input power and saidsecond control circuit for delivering said shutter-opening signalthereto.

9. An electronic shutter system according to claim 8, wherein said thirdmeans includes a photoelectric element and a first capacitor switchablyconnected tosaid source of input power and to said first transistorswitching circuit for controlling the operation thereof in response tothe charge accumulation on said first capacitor in accordance with theimpedance characteristics of said photoelectric element due to the lightimpinging thereon from a photographic object.

10. An electronic shutter system according to claim 9, wherein saidfirst circuit further includes a first switch connected across saidfirst capacitor for shortcircuiting said first capacitor during thegeneration of said shutter-opening signal.

11. An electronic shutter system according to claim 1, wherein saidsecond means comprises a second transistor switching circuit connectedto said first control circuit and said shutter control means forapplying said shutter-opening signal thereto.

12. An electronic shutter system according to claim 11, wherein saidfourth means includes a variable resistor and a second capacitorswitchably connected to a source of input power and to said secondtransistor switching circuit for controlling the operation thereof inresponse to the charge accumulation on said second capacitor. i

13. An electronic shutter system according to claim 12, wherein saidsecond control circuit further includes a second switch connected tosaid second capacitor, for maintaining said second capacitor in apredetermined state of charge during the generation of said shutteropening signal.

14. An electronic shutter system according to claim 13, wherein saidsecond switch comprises a transistor switch, the control electrode ofwhich is connected to said first control circuit, so as to charge anddischarge said second capacitor in response to the output of said firstcontrol circuit.

15. An electronic shutter system according to claim 8, wherein saidsecond means comprises a second transistor switching circuit connectedto said first control circuit and said shutter control means forapplying said shutter-opening signal thereto.

16. An electronic shutter system according to claim 15 wherein saidfourth means includes a variable resistor and a second capacitorswitchably connected to a source of input power and to said secondtransistor switching circuit for controlling the operation thereof inresponse to the charge accumulation on said second capacitor.

17. An electronic shutter system according to claim 16, wherein saidsecond control circuit further includes a second switch connected tosaid second capacitor, for maintaining said second capacitor in apredetermined state of charge during the generation of saidshutteropening signal.

18. An electronic shutter system according to claim 17, wherein saidsecond switch comprises a transistor switch, connected to said firsttransistor switching circuit, for controlling the charging anddischarging of said second capacitor in response to the output thereof.

19. An electronic shutter system according to claim 18, wherein saidthird means includes a photoelectric element and a first capacitorswitchably connected to said source of input power and to said firsttransistor switching circuit for controlling the operation thereof inresponse to the charge accumulation on said first capacitor inaccordance with the impedance characteristics of said photoelectricelement due to the light impinging thereon from a photographic object.

20. An electronic shutter system according to claim 19, wherein saidfirst circuit further includes a first switch connected across saidfirst capacitor for shortcircuiting said first capacitor during thegeneration of said shutter-opening signal.

21. An electronic shutter system according to claim 20, wherein saidshutter control means comprises an electromagnetic means and anenergizing transistor therefor connected together, said energizingtransistor being connected to said second transistor switching circuit,so as to energize and de-energize said electromagnetic means in responseto the output of said second transistor switching circuit.

22. An electronic shutter system according to claim 14, wherein saidtransistor switch is connected across said second capacitor so as tomaintain said capacitor discharged during the generation of saidshutter-opening signal.

23. An electronic shutter system according to claim 14, wherein saidtransistor switch is connected in series with said second capacitor, soas to maintain said second capacitor charged during the generation ofsaid shutter-opening signal.

24. An electronic shutter system according to claim 23, wherein saidfirst transistor switching circuit includes a first and a secondtransistor connected in cascade, the emitter electrode of said firsttransistor being connected to a voltage divider network, the impedanceof which is controllably linked to the diaphragm opening of the lens ofsaid camera and a film sensitivity setting therefor.

25. 'An electronic shutter system according to claim 9, wherein saidfirst control circuit further includes a differential amplifier circuitconnected between said photoelectric element and said first transistorswitching circuit, so as to increase the stability of operation of saidcircuit.

26. An electronic shutter system according to claim 25, furtherincluding a constant current circuit connected between said source ofsupply voltage and said differential amplifier circuit.

27. An electronic shutter system according to claim 26, wherein saidconstant current circuit comprises a pair of cascaded transistors, afirst of which is connected across said source of supply voltage and thesecond of which is connected to said differential amplifier.

28. An electronic shutter system according to claim 26, furtherincluding a film sensitivity setting circuit comprising first and secondtransistors, a first of which is connected between said power source andsaid first capacitor and a second of which is connected between saidpower source and a first input of said differential amplifier.

29. An electronic shutter system according to claim 28, furtherincluding a variable resistor connected between said second transistorof said film sensitivity setting circuit and said first input of saiddifferential amplifier, whereby the first input applied to saiddifferential amplifier is adjusted in dependence of said filmsensitivity.

30. An electronic shutter system according to claim 29, wherein thesecond input of said differential amplifier is connected to said firstcapacitor and said photoelectric element.

31. An electronic shutter system according to claim 30, furtherincluding a first thermal compensation transistor circuit connected tothe input of said first transistor switching circuit for providingthermal compensation therefor.

32. An electronic shutter system according to claim 31, wherein saidsecond means comprises a second transistor switching circuit connectedto said first control circuit and said shutter control means forapplying said shutter opening signal thereto, and further includes asecond thermal compensation transistor circuit connected to said secondtransistor switching circuit for providing thermal compensationtherefor.

1. An electronic shutter system for controlling the opening and closingof a camera shutter comprising: camera shutter control means, connectedto said camera shutter, for effecting the opening and closing thereof; afirst control circuit, including first means, responsive to theapplication of input power thereto, for generating a shutter openingsignal; a second control circuit, connected to said first controlcircuit, including second means, responsive to said shutteropeningsignal, for applying said shutter opening signal to said shutter controlmeans, for effecting the opening of said camera shutter, wherein saidfirst control circuit further includes third means, coupled to saidshutter control means and being responsive to the commencement of theopening motion of said camera shutter by said shutter control means, forgenerating a first timing signal; and wherein said second controlcircuit further includes fourth means, responsive to the generation ofsaid first timing signal by said third means, for generating a secondtiming signal and supplying said second timing signal to said shuttercontrol means, whereby said camera shutter will be closed by theapplication of said second timing signal to said shutter control means,a period of time after the opening thereof.
 2. An electronic shuttersystem according to claim 1, wherein said shutter control meanscomprises an electromagnetic means connected to said shutter and whereinsaid third means of said first control circuit includes a photoelectricelement and a first capacitor connected in series to form a first timingcircuit and being responsive to the brightness of a photographic objectfor controlling the characteristics of said first timing signal.
 3. Anelectronic shutter system according to claim 2, wherein said fourthmeans of said second control circuit comprises a variable resistor and asecond capacitor connected together to form a second timing circuit, thecharging of said second capacitor being controlled by said first timingsignal, anD wherein said second control circuit includes an outputtransistor switching circuit, the output of which is connected to saidelectromagnetic means, responsive to the charge accumulation on saidsecond capacitor, for effecting the energization and de-energization ofsaid electromagnetic means, whereby said shutter will be opened andclosed thereby.
 4. An electronic shutter system according to claim 2,wherein said fourth means of said second control circuit comprises avariable resistor and a second capacitor connected together to form asecond timing signal, the discharging of said second capacitor beingcontrolled by said first timing signal, and wherein said second controlcircuit includes an output transistor switching circuit, the output ofwhich is connected to said electromagnetic means, responsive to thecharge accumulation on said second capacitor, for effecting theenergization and de-energization of said electromagnetic means, wherebysaid shutter will be opened and closed thereby.
 5. An electronic shuttersystem according to claim 2, wherein said third means of said firstcontrol circuit further includes a differential amplifier connected tosaid photoelectric element and coupled to said second control circuit.6. An electronic shutter system according to claim 5, wherein saidoutput transistor switching circuit further includes a compensationtransistor circuit connected thereto for effectively compensating saidoutput switching circuit against temperature variations therein.
 7. Anelectronic switching system according to claim 5, wherein saiddifferential amplifier includes a compensation transistor circuit forprotecting said differential amplifier against the dependency thereof onvariations in the source voltage applied thereto.
 8. An electronicshutter system according to claim 1, wherein said first means of saidfirst control circuit includes a first transistor switching circuitconnected between a source of input power and said second controlcircuit for delivering said shutter-opening signal thereto.
 9. Anelectronic shutter system according to claim 8, wherein said third meansincludes a photoelectric element and a first capacitor switchablyconnected to said source of input power and to said first transistorswitching circuit for controlling the operation thereof in response tothe charge accumulation on said first capacitor in accordance with theimpedance characteristics of said photoelectric element due to the lightimpinging thereon from a photographic object.
 10. An electronic shuttersystem according to claim 9, wherein said first circuit further includesa first switch connected across said first capacitor forshort-circuiting said first capacitor during the generation of saidshutter-opening signal.
 11. An electronic shutter system according toclaim 1, wherein said second means comprises a second transistorswitching circuit connected to said first control circuit and saidshutter control means for applying said shutter-opening signal thereto.12. An electronic shutter system according to claim 11, wherein saidfourth means includes a variable resistor and a second capacitorswitchably connected to a source of input power and to said secondtransistor switching circuit for controlling the operation thereof inresponse to the charge accumulation on said second capacitor.
 13. Anelectronic shutter system according to claim 12, wherein said secondcontrol circuit further includes a second switch connected to saidsecond capacitor, for maintaining said second capacitor in apredetermined state of charge during the generation of said shutteropening signal.
 14. An electronic shutter system according to claim 13,wherein said second switch comprises a transistor switch, the controlelectrode of which is connected to said first control circuit, so as tocharge and discharge said second capacitor in response to the output ofsaid first control circuit.
 15. An electronic shutter system accordingto claim 8, wherein said second means comprises a second transistorswitching circuit connected to said first control circuit and saidshutter control means for applying said shutter-opening signal thereto.16. An electronic shutter system according to claim 15 wherein saidfourth means includes a variable resistor and a second capacitorswitchably connected to a source of input power and to said secondtransistor switching circuit for controlling the operation thereof inresponse to the charge accumulation on said second capacitor.
 17. Anelectronic shutter system according to claim 16, wherein said secondcontrol circuit further includes a second switch connected to saidsecond capacitor, for maintaining said second capacitor in apredetermined state of charge during the generation of saidshutter-opening signal.
 18. An electronic shutter system according toclaim 17, wherein said second switch comprises a transistor switch,connected to said first transistor switching circuit, for controllingthe charging and discharging of said second capacitor in response to theoutput thereof.
 19. An electronic shutter system according to claim 18,wherein said third means includes a photoelectric element and a firstcapacitor switchably connected to said source of input power and to saidfirst transistor switching circuit for controlling the operation thereofin response to the charge accumulation on said first capacitor inaccordance with the impedance characteristics of said photoelectricelement due to the light impinging thereon from a photographic object.20. An electronic shutter system according to claim 19, wherein saidfirst circuit further includes a first switch connected across saidfirst capacitor for short-circuiting said first capacitor during thegeneration of said shutter-opening signal.
 21. An electronic shuttersystem according to claim 20, wherein said shutter control meanscomprises an electromagnetic means and an energizing transistor thereforconnected together, said energizing transistor being connected to saidsecond transistor switching circuit, so as to energize and de-energizesaid electromagnetic means in response to the output of said secondtransistor switching circuit.
 22. An electronic shutter system accordingto claim 14, wherein said transistor switch is connected across saidsecond capacitor so as to maintain said capacitor discharged during thegeneration of said shutter-opening signal.
 23. An electronic shuttersystem according to claim 14, wherein said transistor switch isconnected in series with said second capacitor, so as to maintain saidsecond capacitor charged during the generation of said shutter-openingsignal.
 24. An electronic shutter system according to claim 23, whereinsaid first transistor switching circuit includes a first and a secondtransistor connected in cascade, the emitter electrode of said firsttransistor being connected to a voltage divider network, the impedanceof which is controllably linked to the diaphragm opening of the lens ofsaid camera and a film sensitivity setting therefor.
 25. An electronicshutter system according to claim 9, wherein said first control circuitfurther includes a differential amplifier circuit connected between saidphotoelectric element and said first transistor switching circuit, so asto increase the stability of operation of said circuit.
 26. Anelectronic shutter system according to claim 25, further including aconstant current circuit connected between said source of supply voltageand said differential amplifier circuit.
 27. An electronic shuttersystem according to claim 26, wherein said constant current circuitcomprises a pair of cascaded transistors, a first of which is connectedacross said source of supply voltage and the second of which isconnected to said differential amplifier.
 28. An electronic shuttersystem according to claim 26, further including a film sensitivitysetting circuit comprising first and second transistors, a first ofwhich is connected betweeN said power source and said first capacitorand a second of which is connected between said power source and a firstinput of said differential amplifier.
 29. An electronic shutter systemaccording to claim 28, further including a variable resistor connectedbetween said second transistor of said film sensitivity setting circuitand said first input of said differential amplifier, whereby the firstinput applied to said differential amplifier is adjusted in dependenceof said film sensitivity.
 30. An electronic shutter system according toclaim 29, wherein the second input of said differential amplifier isconnected to said first capacitor and said photoelectric element.
 31. Anelectronic shutter system according to claim 30, further including afirst thermal compensation transistor circuit connected to the input ofsaid first transistor switching circuit for providing thermalcompensation therefor.
 32. An electronic shutter system according toclaim 31, wherein said second means comprises a second transistorswitching circuit connected to said first control circuit and saidshutter control means for applying said shutter opening signal thereto,and further includes a second thermal compensation transistor circuitconnected to said second transistor switching circuit for providingthermal compensation therefor.